The present invention is intended for use in connection with digital cameras, such as pan/tilt/zoom digital cameras that are often used in various types of surveillance applications or video conferencing systems. One example of such a camera is described in U.S. Pat. No. 5,528,289, which describes a method for automatically adjusting a videoconferencing system camera to center an object.
As described in the above reference, a camera provides a digital image to a user. The image is displayed on a monitor display, such as a computer screen, using some kind of application software. The software allows the user to draw a rectangle around an object or area of interest in the displayed image, using a pointer. In response to the user drawing the rectangle, the camera is automatically positioned so as to center the object in the monitor display and adjust the zoom and focus so that the designated area in the rectangle fills the display. The rectangle is drawn by the user by placing the pointer at a desired pointer starting point (PSP), corresponding to a corner of the rectangle, dragging the pointer diagonally across the area of interest, and releasing the mouse button at a pointer ending point (PEP), corresponding to the corner of the rectangle diagonally across from the PSP. Once the rectangle has been drawn, a controller calculates a center point of the rectangle, based on the PEP and the PSP. The controller then calculates a difference between the calculated center point and the midpoint of the monitor display, to determine the pan and tilt of the camera necessary to center the desired picture on the monitor display. Finally, the controller performs a set of calculations to determine how much to zoom to the new field of view, and instructs the camera to focus, either by a focus process or by a memory process, which ends the procedure.
A problem associated with the above approach arises when a user attempts to zoom in on a particular object of interest. Since the rectangle is drawn with the PSP and the PEP in two opposite corners of the rectangle, the likelihood that the user will be able to optimally include the object of interest within the drawn frame is rather low. Often too little or too much of the object of interest is displayed after the zoom, causing the user to repeat the drawing process several times.
U.S. Pat. No. 6,052,110 describes a method for zooming in or zooming out objects that are displayed on a display screen. The user selects a “zoom operation” from a toolbar menu. This causes a cursor to appear on the screen. The user positions the cursor to set a reference point, for example by clicking a mouse button. This causes a reference point indicator to be displayed on the screen. The reference point indicator in the illustrated embodiment is located on the perimeter of a circle. After the reference point has been set, the user can move the cursor away from the reference point. As long as the cursor is within the drawn circle, a zoom out operation occurs, and when the cursor is moved outside the perimeter of the circle, a zoom in operation occurs. The distance between the cursor position and the reference point determines the speed of the zoom operations. No region of interest is specified, and there is no feedback to a camera in this method.